1. Field of the Invention
This invention relates to a method for water leakage prevention in a portion connecting a first pipeline to a second pipeline which branches off from the first pipeline.
2. Description of the Prior Art
A portion connecting a first pipeline, such as a main sewer pipe, to a second pipeline, such as a branch pipe, is generally bonded in a liquid tight manner to each pipeline by means of a bonding agent such as mortar. In general, the bonding agent may be removed from the first or second pipelines by only slightly relatively displacing the pipelines. As a result, a space is formed in the connection portion, and the liquid tightness of the connection portion is lowered. A cut-off treatment is performed to prevent water leakage from the space formed in the connection portion.
This water cut-off treatment is generally performed by a chemical feeding method involving the injection of a cut-off agent of cement or liquid type into the space and around the connection portion and then coagulating the cut-off agent.
The chemical feeding method exhibits the following problems. When water leakage occurs in practice, the cut-off agent is diluted with water, flows into the pipeline, and frequently fails to harden. Consequently, subsequent treatment for removing cut-off agent from the pipeline should also be conducted. In the chemical feeding method using a cement-type cut-off agent, the hardened cut-off agent does not exhibit elasticity. When pipes are displaced due to vibration, land subsidence or the like, the hardened cut-off agent is peeled off from the pipeline, and cracks form therein. As a result, any long-term, stable water cut-off is not expected. In the chemical feeding method using a liquid-type cut-off agent, the mechanical strength of the cut-off agent is low. The water cut-off is therefore not stably maintained for a long period of time.
In order to solve these problems, the present inventors employ cut-off methods utilizing an impermeable cut-off member. This impermeable cut-off member has an expandable hose portion and a flange portion provided integrally with one end of the hose portion, so that the flange portion is in liquid tight contact with the inner surface of the first pipeline. The hose portion of the impermeable cut-off member is in contact with the inner surface of the second pipeline and extends within the second pipeline.
This cut-off member exhibits the advantage of water leakage prevention without using a cut-off agent to close the space formed in the connection portion. Water leakage from a portion of the second pipeline is also prevented.
When the first and second pipelines are of a size such that an operator is unable to enter, it is difficult to dispose the impermeable cut-off member, so that the flange portion is positioned within the first pipeline and the hose portion extends within the second pipeline.